Pope Francis has questioned the claim that Islam should be identified with violence, in contrast to the Islamic State militant group, which he says is a fundamentalist sect of the religion.

"I do not believe it is right to identify Islam with violence," the Pope told journalists during the July 31 papal flight to Rome following his apostolic journey to Poland. "This is not right and it is not true."

"I don't like to speak about Islamic violence," the Pope said, taking into account that one sees violence every day in the newspapers, even at the hands of baptised Catholics.

"There are violent Catholics!" he said. "If I speak of Islamic violence, I must speak of Catholic violence."

The Pope expressed his belief that every religion has its fundamentalist groups, including Catholicism.

Such fundamentalism, when it is present, can "kill with language," he said, citing the worlds of the Apostle James.

Francis' remarks came in response to a question put by a journalist regarding the murder of a French priest at the hands of Islamist militants, an attack which Pope Francis condemned. The journalist asked the Pope why he never refers to Islam when decrying these sorts of terrorist acts committed by Islamist militants.

Fr. Jacques Hamel, 86, was killed Tuesday after two armed gunmen stormed a church in Saint-Etienne-du-Rouvray during Mass. The assailants entered the church and took the celebrating priest and four others hostage.

The Islamic State has claimed responsibility for the attack, which was carried out by Adel Kermiche and Abdel Malik Nabil Petitjean, both 19.

Two more men – Farid K, 30, a cousin of Petitjean, and Jean-Philippe Steven J, 20 – have been placed under formal investigation in connection to the murders, according to the BBC.

During the in-flight conference, Pope Francis explained he had a long discussion with the Al-Azhar University's grand iiman, and so understands Muslims. "They seek peace, encounter," he explained.

Moreover, he said that according to the nuncio to an African nation (which the Pope did not specify in the conference), many of those who pass through the Jubilee Year of Mercy Door, who go to pray at the altar of Our Lady, are Muslims who wish to take part in the Jubilee.

Francis also recalled the Muslims he encountered during last November's trip to the Central African Republic, including the imam who at one point joined him in the popemobile.

Acknowledging that there are fundamentalist groups, the Pope stressed that there are many young people, including Europeans themselves, who "have left empty of ideals, who have no work," and who turn to drugs and alcohol and "enlist in fundamentalist groups."

"One can speak of the so-called ISIS," the Pope continued, "but it is an Islamic state which presents itself as violence."

The group thus shows its "identity card," he said, making reference to the group of Egyptians whose throats were slit on the coast of Libya.

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"This is a small fundamentalist group called ISIS," he said. But "I do not believe it is true or correct that Islam is terrorist."

"Terrorism is everywhere. You think of tribal terrorism of some African countries," he said. "Terrorism grows when there are no other options, and when the center of the global economy is a the god of money and not the person – men and women – this is already the first terrorism!"

"You have cast out the wonder of creation – man and woman – and you have put money in its place. This is a basic terrorism against all of humanity! Think about it!"

Sunday evening's in-flight press conference came at the end of Pope Francis' July 27-31 trip to Poland, where he presided over World Youth Day celebrations in Krakow.